Soil Moisture Content Retrieval in an Arid to Semi-Arid Region in the Xinjiang Province

In the arid and semi-arid regions of the Xinjiang province in Northwestern China, soil moisture content (SMC) controls vegetation growth. With regard to quantifying SMC, the apparent thermal inertia (ATI) approach was applied. This paper focuses on the determination of ATI using day and night land surface temperatures (LST) from locally received MODIS data. The day and night LST difference is a proxy for the calculation of actual ATI. LST estimation is based on an adapted split window method, based on vegetation cover for emissivity estimation. The validation of the MODIS SMC product was performed with TDI probe measurements. TDI probe SMC measurements were performed at the site Kuerle at about monthly intervals. When the SMC time series is compared with the TDI measurements, a satisfactory correspondence can be observed. The ATI approach seems suitable for 1 m depth SMC profile retrievals in the Xinjiang province using MODIS data at 1times1 km² resolution.